- http://docs.moodle.org/19/en/Performance#Apache_performance
"Caching (unsupported) - Please note that this kind of caching may create major problems during upgrades."
- http://docs.moodle.org/20/en/Performance_recommendations#Apache_performance
http://docs.moodle.org/21/en/Performance_recommendations#Apache_performance
http://docs.moodle.org/22/en/Performance_recommendations#Apache_performance
"Caching (unsupported) - Please note that this kind of caching may create major problems during upgrades."
- http://docs.moodle.org/23/en/Performance_recommendations#Apache_performance
"Caching - Apache can be told to make page ..."
- http://docs.moodle.org/24/en/Performance_recommendations#Apache_performance
"Caching (absolutely unsupported, Moodle 1.9 only) Please note that this kind of caching creates major problems during upgrades, you need to remove the caching directives one week before any upgrade."
The background: See the discussion "Caching web pages to enhance performance--where to include directives" https://moodle.org/mod/forum/discuss.php?d=223564 in the "Hardware and Performance" forum.